It was announced in AKB48 Janken Tournament 2016, AKB48 will setup a new sister group "STU48" (瀬戸内48) in 2017 Summer.﻿

STU48 is a sister with no theater Japanese City, [it appears that] their theater is on board [a cruise ship]. STU, short for SeToUchi, is a region of Japan, encompassing the areas of Honshu, Shikoku, and Kyushu that border the Seto Inland Sea.